1. Field of the Invention
The present invention relates to a microstrip structure and, more particularly, to a microstrip structure for isolating adjacent transmission lines from each other so as to reduce the crosstalk interference between the transmission lines.
2. Description of the Prior Art
In recently years, with the package size of electronic products becoming smaller and signal transmission rate becoming higher in the high-frequency circuit or high-speed digital system, electronic circuits tend to be designed to be more intensive or can be operated at high microwave frequency. Accordingly, the crosstalk phenomenon between electronic circuits becomes more serious than ever before. When signals are transmitted via transmission channel, adjacent transmission lines will be interfered by each other due to electromagnetic coupling phenomenon; therefore, the interfered transmission lines may generate coupling voltage and current, which is so-called crosstalk. Excessive crosstalk may influence the efficiency of the system, or result in the mistrigger of the circuit thereby damaging the system. Besides, when designing a bent electronic circuit, engineers usually increase the interval between the adjacent microstrip lines, or increase the rising time or the falling time of the digital signals in order to reduce the crosstalk; however, the crosstalk still cannot be completely eliminated.
As the conventional methods cannot effectively eliminate the crosstalk occurring between the transmission lines, it is necessary to propose novel microstrip structure for isolating microstrip lines from each other thereby suppressing the crosstalk therebetween and reducing the mode conversion effect between differential mode and common mode.